In today’s CAN networks, node-to-node isolation is
increasingly recommended by designers to reduce EMI susceptibility, especially
in high-speed applications. The speed of IsoLoop Isolators minimizes CAN loop
delay to maximize data rate over any given bus length. NVE offers single-chip
isolated CAN transceivers and bidirectional
isolators for use with stand-alone CAN transceivers.

Illustrative applications are as follows:

Isolated CAN Transceiver Reference Design

The IL41050TA single-chip isolated CAN transceiver provides an isolated CAN interface in a single chip. The isolator operates on the 3.3 V microcontroller power supply, and the dc-dc convertor provides 5 V to power the bus side. The IL41050TA can withstand 150 V transients on the bus; the PSM712 provides additional ESD protection if necessary.

An innovative non-volatile programmable power-up feature prevents unstable nodes. A state that needs to be present at node power up can be programmed at the last power down. For example if a CAN node is required to “pulse” dominant at power up, TxD can be sent low by the controller immediately prior to power down. When power is resumed, the node will immediately go dominant allowing self-check code in the microcontroller to verify node operation. If desired, the node can also power up silently by presetting the TxD line high at power down. At the next power on, the IL41050 will remain silent, awaiting a dominant state from the bus.

Isolating Standard
CAN Transceivers

This
simple circuit works with any CAN transceiver with a TxD dominant timeout, which
includes all of the current-generation transceivers including the AMIS-30660 or the Philips/NXP
TJA1050. Propagation delay is critical for CANbus, and the IL712 and IL721 bidirectional
isolators have best-in-class propagation delay of 10 ns typical. This minimizes
CAN loop delay and maximizes data rate over any given bus length, making IsoLoop
Isolators ideal for CAN isolation. NVE also offers the smallest two-channel isolator,
the IL712-1, in a unique MSOP-8.

Isolating Legacy CAN Transceivers

Power-on
reset circuitry allows an IL712 or IL721 to isolate legacy transceivers without
integrated TxD timeout, such as the Philips/NXP PCA82C250.